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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.awt;

import java.util.List;
import java.util.ArrayList;
import sun.util.logging.PlatformLogger;

/**
 * A FocusTraversalPolicy that determines traversal order based on the order
 * of child Components in a Container. From a particular focus cycle root, the
 * policy makes a pre-order traversal of the Component hierarchy, and traverses
 * a Container's children according to the ordering of the array returned by
 * <code>Container.getComponents()</code>. Portions of the hierarchy that are
 * not visible and displayable will not be searched.
 * <p>
 * By default, ContainerOrderFocusTraversalPolicy implicitly transfers focus
 * down-cycle. That is, during normal forward focus traversal, the Component
 * traversed after a focus cycle root will be the focus-cycle-root's default
 * Component to focus. This behavior can be disabled using the
 * <code>setImplicitDownCycleTraversal</code> method.
 * <p>
 * By default, methods of this class will return a Component only if it is
 * visible, displayable, enabled, and focusable. Subclasses can modify this
 * behavior by overriding the <code>accept</code> method.
 * <p>
 * This policy takes into account <a
 * href="doc-files/FocusSpec.html#FocusTraversalPolicyProviders">focus traversal
 * policy providers</a>.  When searching for first/last/next/previous Component,
 * if a focus traversal policy provider is encountered, its focus traversal
 * policy is used to perform the search operation.
 *
 * @author David Mendenhall
 * @see Container#getComponents
 * @since 1.4
 */
public class ContainerOrderFocusTraversalPolicy extends FocusTraversalPolicy
    implements java.io.Serializable {

  private static final PlatformLogger log = PlatformLogger
      .getLogger("java.awt.ContainerOrderFocusTraversalPolicy");

  final private int FORWARD_TRAVERSAL = 0;
  final private int BACKWARD_TRAVERSAL = 1;

  /*
   * JDK 1.4 serialVersionUID
   */
  private static final long serialVersionUID = 486933713763926351L;

  private boolean implicitDownCycleTraversal = true;

  /**
   * Used by getComponentAfter and getComponentBefore for efficiency. In
   * order to maintain compliance with the specification of
   * FocusTraversalPolicy, if traversal wraps, we should invoke
   * getFirstComponent or getLastComponent. These methods may be overriden in
   * subclasses to behave in a non-generic way. However, in the generic case,
   * these methods will simply return the first or last Components of the
   * sorted list, respectively. Since getComponentAfter and
   * getComponentBefore have already built the list before determining
   * that they need to invoke getFirstComponent or getLastComponent, the
   * list should be reused if possible.
   */
  transient private Container cachedRoot;
  transient private List<Component> cachedCycle;

  /*
   * We suppose to use getFocusTraversalCycle & getComponentIndex methods in order
   * to divide the policy into two parts:
   * 1) Making the focus traversal cycle.
   * 2) Traversing the cycle.
   * The 1st point assumes producing a list of components representing the focus
   * traversal cycle. The two methods mentioned above should implement this logic.
   * The 2nd point assumes implementing the common concepts of operating on the
   * cycle: traversing back and forth, retrieving the initial/default/first/last
   * component. These concepts are described in the AWT Focus Spec and they are
   * applied to the FocusTraversalPolicy in general.
   * Thus, a descendant of this policy may wish to not reimplement the logic of
   * the 2nd point but just override the implementation of the 1st one.
   * A striking example of such a descendant is the javax.swing.SortingFocusTraversalPolicy.
   */
    /*protected*/
  private List<Component> getFocusTraversalCycle(Container aContainer) {
    List<Component> cycle = new ArrayList<Component>();
    enumerateCycle(aContainer, cycle);
    return cycle;
  }

  /*protected*/
  private int getComponentIndex(List<Component> cycle, Component aComponent) {
    return cycle.indexOf(aComponent);
  }

  private void enumerateCycle(Container container, List<Component> cycle) {
    if (!(container.isVisible() && container.isDisplayable())) {
      return;
    }

    cycle.add(container);

    Component[] components = container.getComponents();
    for (int i = 0; i < components.length; i++) {
      Component comp = components[i];
      if (comp instanceof Container) {
        Container cont = (Container) comp;

        if (!cont.isFocusCycleRoot() && !cont.isFocusTraversalPolicyProvider()) {
          enumerateCycle(cont, cycle);
          continue;
        }
      }
      cycle.add(comp);
    }
  }

  private Container getTopmostProvider(Container focusCycleRoot, Component aComponent) {
    Container aCont = aComponent.getParent();
    Container ftp = null;
    while (aCont != focusCycleRoot && aCont != null) {
      if (aCont.isFocusTraversalPolicyProvider()) {
        ftp = aCont;
      }
      aCont = aCont.getParent();
    }
    if (aCont == null) {
      return null;
    }
    return ftp;
  }

  /*
   * Checks if a new focus cycle takes place and returns a Component to traverse focus to.
   * @param comp a possible focus cycle root or policy provider
   * @param traversalDirection the direction of the traversal
   * @return a Component to traverse focus to if {@code comp} is a root or provider
   *         and implicit down-cycle is set, otherwise {@code null}
   */
  private Component getComponentDownCycle(Component comp, int traversalDirection) {
    Component retComp = null;

    if (comp instanceof Container) {
      Container cont = (Container) comp;

      if (cont.isFocusCycleRoot()) {
        if (getImplicitDownCycleTraversal()) {
          retComp = cont.getFocusTraversalPolicy().getDefaultComponent(cont);

          if (retComp != null && log.isLoggable(PlatformLogger.Level.FINE)) {
            log.fine("### Transfered focus down-cycle to " + retComp +
                " in the focus cycle root " + cont);
          }
        } else {
          return null;
        }
      } else if (cont.isFocusTraversalPolicyProvider()) {
        retComp = (traversalDirection == FORWARD_TRAVERSAL ?
            cont.getFocusTraversalPolicy().getDefaultComponent(cont) :
            cont.getFocusTraversalPolicy().getLastComponent(cont));

        if (retComp != null && log.isLoggable(PlatformLogger.Level.FINE)) {
          log.fine("### Transfered focus to " + retComp + " in the FTP provider " + cont);
        }
      }
    }
    return retComp;
  }

  /**
   * Returns the Component that should receive the focus after aComponent.
   * aContainer must be a focus cycle root of aComponent or a focus traversal policy provider.
   * <p>
   * By default, ContainerOrderFocusTraversalPolicy implicitly transfers
   * focus down-cycle. That is, during normal forward focus traversal, the
   * Component traversed after a focus cycle root will be the focus-cycle-
   * root's default Component to focus. This behavior can be disabled using
   * the <code>setImplicitDownCycleTraversal</code> method.
   * <p>
   * If aContainer is <a href="doc-files/FocusSpec.html#FocusTraversalPolicyProviders">focus
   * traversal policy provider</a>, the focus is always transferred down-cycle.
   *
   * @param aContainer a focus cycle root of aComponent or a focus traversal policy provider
   * @param aComponent a (possibly indirect) child of aContainer, or aContainer itself
   * @return the Component that should receive the focus after aComponent, or null if no suitable
   * Component can be found
   * @throws IllegalArgumentException if aContainer is not a focus cycle root of aComponent or focus
   * traversal policy provider, or if either aContainer or aComponent is null
   */
  public Component getComponentAfter(Container aContainer, Component aComponent) {
    if (log.isLoggable(PlatformLogger.Level.FINE)) {
      log.fine("### Searching in " + aContainer + " for component after " + aComponent);
    }

    if (aContainer == null || aComponent == null) {
      throw new IllegalArgumentException("aContainer and aComponent cannot be null");
    }
    if (!aContainer.isFocusTraversalPolicyProvider() && !aContainer.isFocusCycleRoot()) {
      throw new IllegalArgumentException(
          "aContainer should be focus cycle root or focus traversal policy provider");

    } else if (aContainer.isFocusCycleRoot() && !aComponent.isFocusCycleRoot(aContainer)) {
      throw new IllegalArgumentException("aContainer is not a focus cycle root of aComponent");
    }

    synchronized (aContainer.getTreeLock()) {

      if (!(aContainer.isVisible() && aContainer.isDisplayable())) {
        return null;
      }

      // Before all the ckecks below we first see if it's an FTP provider or a focus cycle root.
      // If it's the case just go down cycle (if it's set to "implicit").
      Component comp = getComponentDownCycle(aComponent, FORWARD_TRAVERSAL);
      if (comp != null) {
        return comp;
      }

      // See if the component is inside of policy provider.
      Container provider = getTopmostProvider(aContainer, aComponent);
      if (provider != null) {
        if (log.isLoggable(PlatformLogger.Level.FINE)) {
          log.fine("### Asking FTP " + provider + " for component after " + aComponent);
        }

        // FTP knows how to find component after the given. We don't.
        FocusTraversalPolicy policy = provider.getFocusTraversalPolicy();
        Component afterComp = policy.getComponentAfter(provider, aComponent);

        // Null result means that we overstepped the limit of the FTP's cycle.
        // In that case we must quit the cycle, otherwise return the component found.
        if (afterComp != null) {
          if (log.isLoggable(PlatformLogger.Level.FINE)) {
            log.fine("### FTP returned " + afterComp);
          }
          return afterComp;
        }
        aComponent = provider;
      }

      List<Component> cycle = getFocusTraversalCycle(aContainer);

      if (log.isLoggable(PlatformLogger.Level.FINE)) {
        log.fine("### Cycle is " + cycle + ", component is " + aComponent);
      }

      int index = getComponentIndex(cycle, aComponent);

      if (index < 0) {
        if (log.isLoggable(PlatformLogger.Level.FINE)) {
          log.fine("### Didn't find component " + aComponent + " in a cycle " + aContainer);
        }
        return getFirstComponent(aContainer);
      }

      for (index++; index < cycle.size(); index++) {
        comp = cycle.get(index);
        if (accept(comp)) {
          return comp;
        } else if ((comp = getComponentDownCycle(comp, FORWARD_TRAVERSAL)) != null) {
          return comp;
        }
      }

      if (aContainer.isFocusCycleRoot()) {
        this.cachedRoot = aContainer;
        this.cachedCycle = cycle;

        comp = getFirstComponent(aContainer);

        this.cachedRoot = null;
        this.cachedCycle = null;

        return comp;
      }
    }
    return null;
  }

  /**
   * Returns the Component that should receive the focus before aComponent.
   * aContainer must be a focus cycle root of aComponent or a <a
   * href="doc-files/FocusSpec.html#FocusTraversalPolicyProviders">focus traversal policy
   * provider</a>.
   *
   * @param aContainer a focus cycle root of aComponent or focus traversal policy provider
   * @param aComponent a (possibly indirect) child of aContainer, or aContainer itself
   * @return the Component that should receive the focus before aComponent, or null if no suitable
   * Component can be found
   * @throws IllegalArgumentException if aContainer is not a focus cycle root of aComponent or focus
   * traversal policy provider, or if either aContainer or aComponent is null
   */
  public Component getComponentBefore(Container aContainer, Component aComponent) {
    if (aContainer == null || aComponent == null) {
      throw new IllegalArgumentException("aContainer and aComponent cannot be null");
    }
    if (!aContainer.isFocusTraversalPolicyProvider() && !aContainer.isFocusCycleRoot()) {
      throw new IllegalArgumentException(
          "aContainer should be focus cycle root or focus traversal policy provider");

    } else if (aContainer.isFocusCycleRoot() && !aComponent.isFocusCycleRoot(aContainer)) {
      throw new IllegalArgumentException("aContainer is not a focus cycle root of aComponent");
    }

    synchronized (aContainer.getTreeLock()) {

      if (!(aContainer.isVisible() && aContainer.isDisplayable())) {
        return null;
      }

      // See if the component is inside of policy provider.
      Container provider = getTopmostProvider(aContainer, aComponent);
      if (provider != null) {
        if (log.isLoggable(PlatformLogger.Level.FINE)) {
          log.fine("### Asking FTP " + provider + " for component after " + aComponent);
        }

        // FTP knows how to find component after the given. We don't.
        FocusTraversalPolicy policy = provider.getFocusTraversalPolicy();
        Component beforeComp = policy.getComponentBefore(provider, aComponent);

        // Null result means that we overstepped the limit of the FTP's cycle.
        // In that case we must quit the cycle, otherwise return the component found.
        if (beforeComp != null) {
          if (log.isLoggable(PlatformLogger.Level.FINE)) {
            log.fine("### FTP returned " + beforeComp);
          }
          return beforeComp;
        }
        aComponent = provider;

        // If the provider is traversable it's returned.
        if (accept(aComponent)) {
          return aComponent;
        }
      }

      List<Component> cycle = getFocusTraversalCycle(aContainer);

      if (log.isLoggable(PlatformLogger.Level.FINE)) {
        log.fine("### Cycle is " + cycle + ", component is " + aComponent);
      }

      int index = getComponentIndex(cycle, aComponent);

      if (index < 0) {
        if (log.isLoggable(PlatformLogger.Level.FINE)) {
          log.fine("### Didn't find component " + aComponent + " in a cycle " + aContainer);
        }
        return getLastComponent(aContainer);
      }

      Component comp = null;
      Component tryComp = null;

      for (index--; index >= 0; index--) {
        comp = cycle.get(index);
        if (comp != aContainer
            && (tryComp = getComponentDownCycle(comp, BACKWARD_TRAVERSAL)) != null) {
          return tryComp;
        } else if (accept(comp)) {
          return comp;
        }
      }

      if (aContainer.isFocusCycleRoot()) {
        this.cachedRoot = aContainer;
        this.cachedCycle = cycle;

        comp = getLastComponent(aContainer);

        this.cachedRoot = null;
        this.cachedCycle = null;

        return comp;
      }
    }
    return null;
  }

  /**
   * Returns the first Component in the traversal cycle. This method is used
   * to determine the next Component to focus when traversal wraps in the
   * forward direction.
   *
   * @param aContainer the focus cycle root or focus traversal policy provider whose first Component
   * is to be returned
   * @return the first Component in the traversal cycle of aContainer, or null if no suitable
   * Component can be found
   * @throws IllegalArgumentException if aContainer is null
   */
  public Component getFirstComponent(Container aContainer) {
    List<Component> cycle;

    if (log.isLoggable(PlatformLogger.Level.FINE)) {
      log.fine("### Getting first component in " + aContainer);
    }
    if (aContainer == null) {
      throw new IllegalArgumentException("aContainer cannot be null");

    }

    synchronized (aContainer.getTreeLock()) {

      if (!(aContainer.isVisible() && aContainer.isDisplayable())) {
        return null;
      }

      if (this.cachedRoot == aContainer) {
        cycle = this.cachedCycle;
      } else {
        cycle = getFocusTraversalCycle(aContainer);
      }

      if (cycle.size() == 0) {
        if (log.isLoggable(PlatformLogger.Level.FINE)) {
          log.fine("### Cycle is empty");
        }
        return null;
      }
      if (log.isLoggable(PlatformLogger.Level.FINE)) {
        log.fine("### Cycle is " + cycle);
      }

      for (Component comp : cycle) {
        if (accept(comp)) {
          return comp;
        } else if (comp != aContainer &&
            (comp = getComponentDownCycle(comp, FORWARD_TRAVERSAL)) != null) {
          return comp;
        }
      }
    }
    return null;
  }

  /**
   * Returns the last Component in the traversal cycle. This method is used
   * to determine the next Component to focus when traversal wraps in the
   * reverse direction.
   *
   * @param aContainer the focus cycle root or focus traversal policy provider whose last Component
   * is to be returned
   * @return the last Component in the traversal cycle of aContainer, or null if no suitable
   * Component can be found
   * @throws IllegalArgumentException if aContainer is null
   */
  public Component getLastComponent(Container aContainer) {
    List<Component> cycle;
    if (log.isLoggable(PlatformLogger.Level.FINE)) {
      log.fine("### Getting last component in " + aContainer);
    }

    if (aContainer == null) {
      throw new IllegalArgumentException("aContainer cannot be null");
    }

    synchronized (aContainer.getTreeLock()) {

      if (!(aContainer.isVisible() && aContainer.isDisplayable())) {
        return null;
      }

      if (this.cachedRoot == aContainer) {
        cycle = this.cachedCycle;
      } else {
        cycle = getFocusTraversalCycle(aContainer);
      }

      if (cycle.size() == 0) {
        if (log.isLoggable(PlatformLogger.Level.FINE)) {
          log.fine("### Cycle is empty");
        }
        return null;
      }
      if (log.isLoggable(PlatformLogger.Level.FINE)) {
        log.fine("### Cycle is " + cycle);
      }

      for (int i = cycle.size() - 1; i >= 0; i--) {
        Component comp = cycle.get(i);
        if (accept(comp)) {
          return comp;
        } else if (comp instanceof Container && comp != aContainer) {
          Container cont = (Container) comp;
          if (cont.isFocusTraversalPolicyProvider()) {
            Component retComp = cont.getFocusTraversalPolicy().getLastComponent(cont);
            if (retComp != null) {
              return retComp;
            }
          }
        }
      }
    }
    return null;
  }

  /**
   * Returns the default Component to focus. This Component will be the first
   * to receive focus when traversing down into a new focus traversal cycle
   * rooted at aContainer. The default implementation of this method
   * returns the same Component as <code>getFirstComponent</code>.
   *
   * @param aContainer the focus cycle root or focus traversal policy provider whose default
   * Component is to be returned
   * @return the default Component in the traversal cycle of aContainer, or null if no suitable
   * Component can be found
   * @throws IllegalArgumentException if aContainer is null
   * @see #getFirstComponent
   */
  public Component getDefaultComponent(Container aContainer) {
    return getFirstComponent(aContainer);
  }

  /**
   * Sets whether this ContainerOrderFocusTraversalPolicy transfers focus
   * down-cycle implicitly. If <code>true</code>, during normal forward focus
   * traversal, the Component traversed after a focus cycle root will be the
   * focus-cycle-root's default Component to focus. If <code>false</code>,
   * the next Component in the focus traversal cycle rooted at the specified
   * focus cycle root will be traversed instead. The default value for this
   * property is <code>true</code>.
   *
   * @param implicitDownCycleTraversal whether this ContainerOrderFocusTraversalPolicy transfers
   * focus down-cycle implicitly
   * @see #getImplicitDownCycleTraversal
   * @see #getFirstComponent
   */
  public void setImplicitDownCycleTraversal(boolean implicitDownCycleTraversal) {
    this.implicitDownCycleTraversal = implicitDownCycleTraversal;
  }

  /**
   * Returns whether this ContainerOrderFocusTraversalPolicy transfers focus
   * down-cycle implicitly. If <code>true</code>, during normal forward focus
   * traversal, the Component traversed after a focus cycle root will be the
   * focus-cycle-root's default Component to focus. If <code>false</code>,
   * the next Component in the focus traversal cycle rooted at the specified
   * focus cycle root will be traversed instead.
   *
   * @return whether this ContainerOrderFocusTraversalPolicy transfers focus down-cycle implicitly
   * @see #setImplicitDownCycleTraversal
   * @see #getFirstComponent
   */
  public boolean getImplicitDownCycleTraversal() {
    return implicitDownCycleTraversal;
  }

  /**
   * Determines whether a Component is an acceptable choice as the new
   * focus owner. By default, this method will accept a Component if and
   * only if it is visible, displayable, enabled, and focusable.
   *
   * @param aComponent the Component whose fitness as a focus owner is to be tested
   * @return <code>true</code> if aComponent is visible, displayable, enabled, and focusable;
   * <code>false</code> otherwise
   */
  protected boolean accept(Component aComponent) {
    if (!aComponent.canBeFocusOwner()) {
      return false;
    }

    // Verify that the Component is recursively enabled. Disabling a
    // heavyweight Container disables its children, whereas disabling
    // a lightweight Container does not.
    if (!(aComponent instanceof Window)) {
      for (Container enableTest = aComponent.getParent();
          enableTest != null;
          enableTest = enableTest.getParent()) {
        if (!(enableTest.isEnabled() || enableTest.isLightweight())) {
          return false;
        }
        if (enableTest instanceof Window) {
          break;
        }
      }
    }

    return true;
  }
}
